1. Field of the Invention
The present invention relates to a perpendicular recording thin-film magnetic head and a method of manufacturing the same.
2. Related Background Art
As hard disk drives, those of in-plane recording type in which a recording layer of a magnetic recording medium is magnetized in its in-plane direction so as to effect magnetic recording have already been in widespread use. For achieving a higher recording density, attention has been directed to perpendicular recording hard disk drives which perform magnetic recording by magnetizing a recording layer of a magnetic recording medium in a direction orthogonal to its in-plane direction. The perpendicular recording scheme has been considered advantageous over the in-plane recording scheme in achieving hard disk drives having a high recording density, since it can increase the volume per bit of a magnetic material constituting the recording layer of the magnetic recording medium, for example.
A perpendicular recording thin-film magnetic head employed in the perpendicular recording scheme comprises a main magnetic pole which emits a magnetic flux from a medium-opposing surface to a magnetic recording medium, and a return yoke into which the magnetic flux having magnetized the medium after being emitted from the main magnetic pole flows. The main magnetic pole has a sharpened tip part exposed at the medium-opposing surface and a base part which is wider than the tip part. Since the magnetic flux pumped by a coil layer so as to pass through the base part is concentrated at the tip part of the main magnetic pole, the main magnetic pole can emit a strong magnetic flux toward the magnetic recording medium. The magnetic flux emitted from the main magnetic pole passes perpendicularly through the recording layer so as to be drawn to a soft magnetic backing layer under the recording layer of the magnetic recording medium, thereby magnetizing the recording layer perpendicularly. The magnetic flux transmitted through the recording layer passes the soft magnetic backing layer in its in-plane direction and then perpendicularly through the recording layer again, so as to flow into the return yoke. Thus, the main magnetic pole, soft magnetic backing layer, and return yoke construct a magnetic circuit, whereby the perpendicular recording thin-film magnetic head performs perpendicular magnetic recording onto the magnetic recording medium.
For improving the recording performance by such a perpendicular recording thin-film magnetic head, it is necessary to restrain a phenomenon known as side erase from occurring. The side erase is a phenomenon in which, at the time of magnetic recording, information recorded on a track adjacent to a track to be recorded in a magnetic recording medium is erased unintentionally. This phenomenon occurs because magnetic fluxes are emitted from side faces of the tip part or side faces of the base part in the main magnetic pole toward tracks adjacent to the track to be recorded, for example. For suppressing such occurrence of side erase, perpendicular recording thin-film magnetic heads equipped with a side shield which is a magnetic shield layer arranged along the medium-opposing surface so as to hold the tip part of the main magnetic pole in the track width direction have been known (see Japanese Patent Application Laid-Open Nos. 2004-127480 and 2005-190518 and U.S. Pat. Nos. 4,656,546, 4,935,832, 6,954,340, and 7,042,682). The side shield absorbs, among magnetic fluxes emitted from the main magnetic pole, those emitted toward tracks adjacent to the track to be recorded, so as to restrain the side erase from occurring, whereby the track density can be improved.
However, there have been cases where the conventional perpendicular recording thin-film magnetic heads equipped with the side shield fail to fully absorb the magnetic fluxes emitted from the main magnetic pole toward tracks adjacent to the track to be recorded in the magnetic recording medium and thus cannot fully suppress the occurrence of side erase. For achieving a perpendicular recording thin-film magnetic head adapted to a high recording density, it is necessary to reduce the throat height, which is the height of the tip part of the main magnetic pole, in particular. When the throat height is made smaller, the distance from the side faces of the base part of the main magnetic pole to the magnetic recording medium becomes shorter, which makes it more difficult for the side shield to fully absorb the magnetic fluxes emitted from the side faces of the main magnetic pole toward tracks adjacent to the track to be recorded in the magnetic recording medium, whereby the occurrence of side erase is hard to suppress sufficiently.
In view of such a problem, it is an object of the present invention to provide a perpendicular recording thin-film magnetic head which can fully suppress the occurrence of side erase, and a method of manufacturing the same.